In general, printing of digital data involves processing input printing data so as to generate printable image data that then can be forwarded to the printing equipment carrying out the actual printing (i.e. a “printer”). In this way, the printing equipment can process the printable image data directly so that no further substantial data processing is required. The printing equipment receives the printable image data and can directly proceed to controlling the means that carry out printing.
For example, the printable image data is used in real time to control a laser or an LED-array for exposing a light-sensitive drum which, in turn, transfers toner particles to the printing medium (e.g. paper, plastic sheets, fabrics, and the like). Likewise, the nozzles of an ink-jet print head can be controlled from the printable image data. In other words, the printable image data allows the printing equipment to fulfill printing in the timely order as required by the moving parts, such as the position of a transfer drum or an ink-jet print head.
Whilst most consumer and office printing equipment is in the form of sheet printers (sheet laser printers, sheet ink-jet printers, and the like), these printers usually execute printing jobs on a sheet basis implying that printable image data needs to be present at least for one page before printing of that page can actually initiated. If input data of one printing job is delayed or the generation of corresponding printable image data is delayed, conventional printers usually pause, after the printing of last page for which printable image data was available has completed, and temporarily stop printing. The printing job can be resumed once corresponding and necessary input data has been received and the corresponding printable image data for a subsequent page has been generated. In other words, conventional printers need to have printable image data ready for at least one page, since one page is printed at a time, and pausing the printing process after one page is possible whilst pausing is difficult during printing one page.
Large-scale printing is essentially effected by similar techniques, i.e. by transferring toner particles or ink droplets from a drum or, respectively, an ink-jet nozzle to the printing medium. However, since large-scale printing processes much more medium in time as compared to the above described consumer and office solutions, the employed mechanisms and equipment still differs substantially. Both the above-mentioned sheet-to-sheet or roll-to-sheet printing as well as the roll-to-roll printing are common in large-scale printing applications. Both printing mechanisms require a high-speed throughput of the printing media and a high speed printing process itself. Considering the involved individual components of the printing equipment, such as conveyor drums, transfer drums, fixation, drying and cooling drums, and the like, it becomes clear that a substantial amount of moving/rotating momentum is involved during large-scale printing equipment is in operation.
In the case of roll-to-roll (respectively roll-to-reel) printing, it is further clear that both the input as well as the output roll (resp. reel) possess considerable momentum during operation, so that both acceleration and deceleration to an operation speed or from an operation speed to a hold requires substantial time. In all, a printing job in large-scale printing machines cannot be easily interrupted without disrupting the printing output, requiring a considerable time for decelerating the involved components and for re-starting them after the printing job is to resumed, and causing waste of printing medium.
As a consequence, large-scale printing usually requires the execution of a printing job in one go, meaning that one printing job is finished without interrupting the process by, for example, holding the involved components. However, the necessity for continuously printing without the possibility to pause requires in turn that the printable image data is available for the printing equipment at the given time. In other words, the means that carry out the actual printing need to be fed with the right printable image data at the right time. If there is a delay in providing the printable image data or if there is a disorder in that data, then probably discontinuity or disorder failures may occur which may result in the need to disregard the output of the entire printing job.
At the same time, large-scale printing usually prints identical or similar (related) images in large numbers onto the printing medium. Industrial large-scale printing finds usually its applications in printing one document many times, one image layout (packaging) many times, or related images in considerable numbers. The latter images may be related but—on an individual basis—still different, in the sense of comprising a constant part which is the same for all images and an individual part that varies with the images. Such images can be used, for example, printing authenticity certificates having a common part and an individual part making each certificate unique, for example, by means of a serial number, individual encoded keys, numbers, characters, or one- or two-dimensional and the like.
Common to these above-mentioned large-scale industrial applications is that a plurality of images are printed in an ordered grid so that the printing output can later be cut into the individual sheets, packagings, certificates, or stamps. If the images are individualized, it is usually required to maintain the order so that in the sense of maintaining their physical arrangement order relative to the medium with regard to the corresponding encoded identifier (e.g. serial number and the like).
Due to the above described need for having all the necessary printable image data ready before a printing job can be initiated, conventional methods usually employ generating all the necessary data before the actual printing job is initiated. In this way, it can be ensured that the data is ready when needed so that the printing job needs not to be interrupted. However, this results in a substantial delay in commencing the printing job, since the printable image data need to be generated beforehand. In summary, these conventional concepts result in a low time efficiency and inefficient resource usage. There is therefore a need for improved methods, apparatuses, systems, that allow for a more efficient handling of large-scale printing as compared to the conventional arts.